Recovery of wool by carbonization



Patented Apr. 16, 1940 UNITED STATES PATENT OFFlCE- RECOVERY h WOO L BY GARBONIZATION Colver P. Dyer, Winchester. Mass., assignor, by mesne assignments, to Monsanto Chemical Company, a corporation of Delaware No Drawing. Application March 3, 1937, Serial No. 128,819. Renewed February 28, 1940 10 Claims.

This invention relates to improvements in the carbonization-of raw wool, cloth or shoddy for the removal of vegetable matter such as burrs,

' cotton thread or other cellulose material so that the finished woolen goods may have a uniform l5 the wool or cloth in a relatively weak sulfuric acid solution after which it is dried and baked to decompose the cellulose particles causing them to be brittle and friable so that these foreign particles can be dusted from the wool by suitable mechanical action. Wool is also carbonized by treatment with aluminum chloride solutions followed by drying and baking.

Some carbonizers, particularly those reclaiming shoddy, prefer dry carbonizing, which is carried out with hydrochloric acid vapor. This vapor is usually generated by dropping strong hydrochloric acid into a retort heated to about 1000 F. and is then allowed to enter a container in which the wool or shoddy has been previously placed. The hydrochloric acid vapor may also be generated by other well known means, such as from salt and sulfuric acid. The dry carbonizing is usually carried out in a chamber some feet each way and 14 feet deep in which a cylinder containing some 1000# of wool stock or shoddy is rotated continuously. Before any gas is allowed to enter this cylinder, the wool is thoroughly dried with hot air, a factor which is essential to the successful carbonization under existing processes. The air is then shut off and hydrochloric acid gas is allowed to enter the chamber which is maintained at about 66 C. The cotton thread in the case of shoddy is rendered brittle by the action of the acid gas so that it can be readily dusted out of the wool. From 3 to 8 hours are requiredto complete one cycle from the time the shoddy is charged until it is ready to be rernoved from the cylinder.

Dry carbonizing as now carried out is inclined to be a troublesome \process because of the mechanical dimculties involved and is rarely used with piece goods or even with raw wool.

In the manufacture of cloth, carbonization is usually carried out in the piece either before or 55 after dyeing. If done before dyeing resists Shoddy must be freed of cot/ ton threads. This is now done by submergi rfg often appear in the dyed piece. These resists are believed to caused by uneven distribution of the sulfuric cm or by unequal acid strengths in' the cloth, rought about bythe manner in which the 6601 is handled mechanically. While 5 common cloth carbonized with sulfuric acid, these r 1sts also exist to a much lesser extent treated by other known processes, for lo, the aluminum chloride process.

en the piece goods are carbonized with acid l0 or with aluminum chloride, after dyeing, the

; shade of the dye is often changed by the treatment with the acid; therefore, in such treatments dyes must be selected with great care so that this change of shade will not occur.

An object of the present invention is to carbonize loose wool, shoddy or piece goods with hydrochloric acid gas in such amanner that the carbonizing process can be carried out in a relatively simple apparatus either continuously or in -a batch process, thus avoiding the more complicated apparatus necessary under present practice.

Another object of the invention is touniformly distribute the carbonizing acid vapors throughout the wool with elimination of resists or other dyeing defects. It is also an object of this invention to carbonize the wool'so that it is uniformly white and is in no way weakened by the acid vapor treatment.

. In accordance with the process ofthis invention the raw wool, cloth or shoddyis brought into contact with air of a. controlled and desired relative humidity. Since there is a well-known relationship between the relative humidity of the air and the moisture content of the wool, or cellulo'sefibres in contact withit, a known and controllable moisture content can be readily imparted to the wool.- This may be carried out by any of the means well known to those skilled 40 in the art such as by the use of a conditioning chamber in which the relative humidity of the air is controlled by automatic means.

The wool, cloth or shoddy is then introduced into a suitable chamber either continuously or on a batch basis. comparatively dry hydrochloric acid gas of any desired concentration can then be introduced and the moisture in the wool will absorb uniformly and rapidly enough of thisgas to form a constant boiling mixture which normally .consistsof' a mixture of 80% water and 20% hydrogen chloride. The hydrogen chloride absorbed by the moisture in the wool and in the cellulose impurities renders the cellulose friable at relatively low temperatures in a comparatively short time. The cellulose is not blackened to any appreciable extent in this process and the wool itself is not weakened nor is it discolored excessively.

The cloth may then be freed of its excess hydrochloric acid content by drying with large volumes of warm air, by neutralization or by the usual known methods. In some instances, namely, if scouring follows carbonization, the burrs may be removed and the excess acid rendered harmless by passing from the carbonizing chamber directly into the scouring bath.

This invention is essentially the impregnation of wool and cellulose fibres with known and controlled amounts of moisture by bringing the material to be treated into contact with air of a known and controlled relative humidity followed by the absorption of HCl by this moisture to give a strength of acid in the fibres of. the cellulosesuitable for rendering these cellulose materials friable. The temperature necessary for promoting the reaction between the hydrochloric acid and the cellulose may be imparted either during or subsequent to the absorption period. The excess acid may be removed after carbonization by redrying with large volumes of air or by methods of neutralization now commonly employed for neutralizing cloth after carbonization. The friable cellulose material is removed by the usual mechanical methods or by the action of the scouring bath as described.

The following figures given by Barker in his book, Wool a Study of the Fibre, show the amount of moisture absorbed by wool and cotton at different relative humidities. It is understood that these figures vary somewhat depending on the type of wool being treated but are substantially as shown.

The'moisture content necessary to accomplish the proper absorption of H01 and subsequent carbonization will vary depending on the type of material being treated and temperatures of carbonization employed; the more difllcult the cellulose is to carbonize the higher the moisture content necessary. Twelve to fifteen per cent of moisture inthe wool is preferred, but higher or lower proportions may lie employed. After 'hav ing acquired the desired amount of moisture in a humidity chamber of suitable design, the wool, cloth or shoddy is'introduced into an absorbing chamber continuously or intermittently and HCl gas having a partial pressure of from 40 mm. to 760 mm. or more is run in. The amount of moisture introduced with the gas is immaterial provided it is under that amount which will cause condensation of liquid hydrochloric acid solution as droplets on the walls or contents of the absorption chamber thus causing spotting of the goods or excess corrosion of the walls of the chamber. The percentage of water by volume in the gas is controlled between the limits of 0 and- 15%, but should special cases warrant, larger proportions of water vapor may be used in the gases introduced into the absorbing vessel.

The hydrochloric acid gas is rapidly absorbed I by the moisture contained in the wool and cellulose materials. Water has a great aih'nity for hydrogen chloride up to the constant boiling mixture of 20% HCl so that no matter how small thewith the cloth. The design of such apparatus is well understood in the textile industry. When the rate of gas input is so controlled that only sufiicient hydrogen chloride is introduced into the chamber to form the 20% HCl liquid with the waterintroduced with the wool, substantialy no hydrogen chloride will be lost in the air being exhausted from the apparatus.

In this invention the hydrogen chloride input is preferably balanced against the water in the wool so that substantially 20% acid is formed in the cloth or shoddy and substantially no hydrogen chloride is vented to the atmosphere. Should more than this amount of hydrogen chloride be introduced into the absorption chamber thepercentage of hydrogen chloride in the cloth will increase to a point determined by the partial pressure of hydrogen chloride in the gas. The strength of the acid can be readily determined .by reference to the published partial pressure data for hydrogen chloride and water in the International Critical Tables. In any case if excess hydrogen chloride is fed into theabsorption chamber, some hydrogen chloride will be exhausted into the atmosphere. If the partial pressure of the hydrogen chloride is less than that inequilibrium with 20% liquid hydrochloric acid no change in the 20% liquid acid strength in the fibre will occur. If the partial pressure is greater than that in equilibrium with 20% acid the strength of liquid acid in the fibres will increase and in this case carbonization of the cellulose will be increased in intensity, requiring lower temperatures or shorter times for decomposing the cellulose. In this last case, however, the excess hydrogen chloride must be recovered or recirculated to prevent contamination of the surrounding atmosphere.

Control of the relative humidity of the air in the impregnating chamber, control of the gas feed so that'substantially no hydrogen chloride escapes to the atmosphere as indicated by the odor or chemical test of the exit gases from the absorption chamber, and control of the temperature and time of the reaction chamber to give the degree of carbonization desired are all that is necessary to keep this process operating uniformly, when used either as a continuous or batch operation.

As previously pointed out the first step in this invention is impregnation of the cloth with controlled amounts of moisture, the second step the' absorption of hydrogen. chloride in the water held by the cloth and the third step the subjection ofthe cloth containing the 20% acid solution to the proper conditions of time and temperature for carbonization of the particular cellulose material being treated. .The second and third steps of this process may be carried on in the same chamber or in separate chambers and either or both operations may be conducted as continuous or batch processes. By appropriate adjustment of detria smasaseanm steps sate partial pressure of substantially 600 mm. is required and even then the cotton thread is badly blackened and the wool 'discolored. With my ing wet out in water, thus obviating large expenditures for drying. A wide variation in hydroinvention by first impregnating the cloth with from substantially'820% water by bringing the cloth into contact with air of controlled relative humidity at the proper temperature, and then carrying out the absorption and carbonization cycles either separately or simultaneously the cotton is rendRrdwery friable in less than ten minutes at 50 CRa ni remains perfectly white.

Burrs which in ordinary carbonizing processes are difficult to handle are readily carbonized in twenty minutes at 65 C. or in ten minutes at 100 To the practical carbonizer the advantages resulting from this invention are obvious. The apparatus is simple and with certain types of wool, rubber covered construction can be used. The time and temperature for carbonizing arerespectively short and low. The process is well ad pted to continuous or batch operation. The abs%rpa bil-QEHWEJ amen contacting itsnths nratmesaliersz ieeaer armeasm mditmhrdmeem air prifieclssatdfli s menammstnmmnmtmmisr al issub eta aw the: pmnerzeoeeainnamstimsamoteiawaisit for carboni 2. The method of carbonizing a material comprising wool and a cellulosic substance characterized in that the material is impregnated uni-- formly throughout with hydrochloric acid containing approximately hydrogen chloride by uniformly impregnating the material with moisture and then absorbing hydrogen chloride there- 3. The method of rendering cellulosic substances in a wool containing material friable in which the material is uniformly impregnated with a controlled quantity of moisture, hydrogen chloride gas is absorbed in the moisture, and the material is subjected to carbonizing conditions.

4. The method of carbonizing a material comprising'wool and a cellulosic substance wherein the material is uniformly impregnated with moisture by contacting it with an atmosphere of controlled humidity, hydrogen chloride is absorbed in the moisture, and the material is carbonized at av temperature of from 40-100 C. for a time of from five to sixty minutes.

'5. The method of rendering cellulosic subtion and carbonization steps may be separated dw in 3 W001 containing terial fr able in combined as one operation. The wool is but slightly discolored, the cotton threads remain perfectly white after carbonization, and diflicult burrs are rendered readily friable. Impregnation by both moisture and hydrochloric acid gas in the vapor phase results in uniform distribution of both of these substances in the wool which, par-- ticularly in the case of cloth, is essential for a.

good non-resisted dyeing. The wool can go through the entire process if desired without bechloric acid gas strength is allowable.

As a source of hydrochloric acid gas any of the well-knownmethods of generation are acceptable provided the moisture content is not suflicient to cause droplet condensation of the hydrochloric acid from the vapor phase. For example, such sources may be commercial dryhydrochloric acid gas, blowing air through 20 B. commercial acid in a suitable stripping column, passing mixtures of hydrochloric and sulfuric acids down asuitable column and adding water to chlorosulfonic acid or to sulfur chloride.

From the foregoing description it will be evident that I have provided a method of carbonizing wool containing materials, whereby the cellulosic substances present may 'be removed which avoids to a very large extent the difficulties thathave been experienced heretofore. It will also be apparent that while I have set forth in detail the various conditions which I have found togive the desired results and haveindicated the variations which may be employed in practicing the invention, the invention in its broad aspect is not limited to the conditions specifically enumerated, but rather contemplates a process according to which carbonization is effected by the so-called dry hich the material is uniformly impregnated with a controlled quantityof moisture, hydrogen chloride gasss absorbedin the moisture, and the material is cafla nized at a temperature of from -l00 C. for a time of from five to sixty min-- utes.

6. The method of rendering cellulosic substances in a wool containing ma erialfriable in which the material is uniformly pregnated with from 12-15% moisture, hydrogen chloride gas is absorbed in the moisture, and the material is subjected to carbonizing conditions.

'7. The improvement in the process of carbon-- izing wool containing cellulosic substances, characterized in that the material to be carbonized is subjected to the action of hydrogen chloride un-' der conditions whereby the hydrogen chloride is absorbed by moisture uniformly contained on the fibres of the material being carbonized, the amount of moisture present having been adjusted to facilitate rapid absorption andcarbonization on the one hand, but insufficient to produce droplets of liquid muriatic acid on the other.

8. The improvement in the process of carbonizing wool containing cellulcsic'substances, characterized in that the material to be carbonized is subjected to the action of hydrogen chloride under conditions whereby the hydrogen chloride is absorbed by moisture uniformly contained on the fibres of the material being carbonized, the material having been first treated with moist air, whereby the desired moisture content is adjusted to facilitate rapid absorptionand uniform carbonization on the one hand but insufficient to produce droplets of liquid muriatic acid on the oigier, before said treatment with hydrogen chlon e.

9. The improvement in the process of carbonutes, to effect carbonization of the cellulosic substances.

10. The improvement in the process of carbonizing wool containing cellulosic substances, characteri'zed in that the material to be 'carbonizedis subjected to the action'of hydrogen chloride un der conditions whereby the hydrogen chloride is I absorbed by moisture uniformly contained onthe fibres of the material being carbonized, the

amount of moisture present being approximately 12-15% and the amount of hydrogen chloride added being not substantially in excess of that required to produce a. constant boiling mixture with the moisture present. 4

COLVER P. DYER. 

